Method of controlling undesirable plant growth



United States Patent 3,360,356 METHOD OF CONTROLLING UNDESIRABLE PLANTGROWTH Joseph F. Vartiak, Naperville, Ill., assignor to Nalco ChemicalCompany, Chicago, 111., a corporation of Delaware No Drawing. Filed May27, 1964, Ser. No. 370,691 3 Claims. (Cl. 71-65) The inst-ant inventionrelates to an improved method of inhibiting growth and reproduction ofnoxious vegetation. More specifically, the present invention relates toan improved method of destroying undesirable vegetation by spraytechniques.

The use of herbicides to control and inhibit undesirable weed growth iswell-known and of widespread usage in the agricultural, industrial, anddomestic fields. Roadsides, embankments, railway right-of-ways, andother earth surfaces are often subjected to treatment with toxicchemicals, organic and inorganic. Numerous compounds with widely variantfunctionalities are effective to a greater or lesser degree ininhibiting or destroying the growth of undesirable vegetation.

Noxious plants or weeds which interfere with human operations broadlyinclude broad leaf plants and grasses. Herbicides have been tailored todestroy or inhibit the growth of both of these or a single group. Insome instances, mixtures of herbicidally active components are employedto combat various species of pervasive type plants.

One of the most widely used techniques in eradicating undesirable weedgrowth is accomplished by spraying the herbicidally active chemical uponthe area within which the plants are growing. In some instances,pre-cmergence spraying is carried out. That is, suspected areas of weedgrowth are sprayed in early spring or late fall to prevent even anappearance of noxious plants or at the least to severely weaken theirgrowth patterns. One of the most effective ways of carrying out a weedcontrol program is spraying the area under control from moving vehicles.As just one example, it is a common practice to spray railwayright-of-ways from a moving train.

Certain problems arise in connection with a herbicidal spray program.First, and foremost, is the problem of misting or fogging whichgenerally begins to occur at a spray pressure of 15 psi and worsens asspray pressures are increased. The herbicidal spray tends to drift andmany valuable crops can be destroyed or damaged to varying degrees. Insome instances, due to extreme toxicity of certain herbicides, evenvaluable animal life such as livestock can be injured. The problem ofdrift has become more widespread in recent years, due to both the moreextensive use of herbicides, as well as application of these herbicidesas concentrated solutions in low volumes per acre.

Generally, undesirable drift from spraying of herbicidal solutions mayoccur in two ways. First, spray drift may occur as a result of thesmaller droplets in the spray being carried away from the target by windor convection currents. Second, the vapor from a volatile herbicide maybe carried away from the target area during or after the spraying in atype of phenomenon called vapor drift. This is most likely to occur inhot weather and can take place even in the absence of wind.

Efforts to substantially reduce spray and vapor drift have in the pastgenerally been unsuccessful or impractical. To minimize drift, sprayingmay be carried out only on days when there is negligible air movement.Such practice is impractical and substantially inhibits overallefiiciency of a herbicidal control program. Likewise, efforts to reduceundesirable misting or fogging by specific design of nozzles has metwith only limited success, and even in such cases requires animpractical sophisticated mechanical design. Lowering the spray pressuredoes aid to some degree in preventing drift. However, sound economics ofa herbicidal spraying operation consistent with good weed control do notallow too great a reduction in spray pressures.

It would therefore be a considerable advance in the herbicidal art if anew and novel method of spraying herbicidally active chemicals wasdevised, whereby undesirable drift was substantially reduced or evendone away with entirely as a problem. If a stream of herbicide chemicalcould be sprayed from solution form, on exact target without substantialmisting or fogging simultaneously taking place, considerable benefitswould accrue. Particularly, desirable animal and plant life could bepreserved without any decrease in efficiency of eradicating noxiousvegetation. Moreover, if such method could be carried out withoutsacrificing operational speed of present herbicidal spray methods,widespread use of such an improved process would be feasible.Specifically, if spray techniques could be carried out at relativelyhigh pressures without fear of misting or fogging, it would be avaluable tool to 'the overall field of herbicide control. Lastly, if theproblem of misting or fogging were done away with in spraying herbicidesdissolved or dispersed in a variety of liquid carriers such as water,oils, etc., such versatile process would become widely adapted in anyconventional herbicide spray program.

It therefore becomes an object of the invention to provide an improvedmethod of spraying liquids whereby misting or fogging tendencies ofthese liquids are substantially reduced.

Another object of the invention is to provide an improved method ofinhibiting the growth and reproduction of noxious plants by sprayingherbicidal liquids within the area to be controlled.

A specific object of the invention is to provide an improved method ofspraying herbicidal liquid concentrates which may be adapted for use inspraying herbicides carried in both hydrophobic and hydrophilic typesolvents.

Other objects will appear hereinafter.

In accordance with the invention an improved method of controlling thegrowth of undesirable vegetation has been discussed. In its broadestaspect this invention is involved with modification of the conventionalprocess of spraying with a solution containing a herbicidal component.The improvement of this process which constitutes the gist of theinvention comprises spraying a herbicidal solution in presence of apolymer which is soluble in the herbicidally active solution in at leastuse dosages. Under suchconditions the misting tendencies of theherbicide liquid when sprayed are substantially reduced. Spray or vapordrift which normally occurs during a high pressure spray operation issubstantially reduced, and in some instances completely obviated.

An important concept of the invention is to carry out the primary objectof reducing misting or fogging of spray solutions by appropriateincorporation of polymer reagent, but without substantially increasingthe viscosity of the solution after polymer dissolution. It has beendiscovered that this can be accomplished in the practices of the instantinvention, since only relatively minute amounts of polymer need bepresent to accomplish the object of mist or fog cont-r01. If theviscosity of the polymer-treated herbicidal liquid is markedly increasedseveral drawbacks are inherently present. First, undesirable plugging ofherbicidal solution in spray nozzles may occur. Also, substantialviscosity increases of a treated herbicidal liquid would cause severepumping problems.

Another deficiency in use of viscous herbicidal concentrates would be amarked decrease in volume of spray solution per unit of time which canbe efficiently sprayed upon the situs to be controlled. Other drawbacksin application of a viscous solution via spray techniques willvegetation may be done away with by following the thus describedinvention.

The anti-misting polymer may be added to any type of solution containinga wide variety of herbicidally active chemicals. These chemicals aregenerally applied be apparent to those skilled in the art. It is thus aprimary in solution form in one of the fol el forms! achievement in theinvention to be able to carry out the W e O OI -In-Water emulsions, andwater-m-oil emulanti-misting or anti-fogging control with relatively noin- 8mm. By the term aqueous solution is meant a solution crease insolution viscosity of herbicide solutions. eohtalhlhg a lh'edomlhehtPortloh of e In addltloh to h process of h invention may b i d t i 10 aherbicidal component as well as an oil-in-water emula wide variety ofdifferent techniques. For example, the SlOh- In most lhstahees the Watereempoheht eemprlses polymer may b inter-dispersed i h h Spray f a atleast 50% by welght of the solution, and more often separate polymerource during the actual praying opat least 60%. In case all BQUCPUIShfbl0ldll SOllltlOIl 1S eration itself. Likewise, the polymer treatingagent may to be treated as {iefihed above, 1t greatly Preferred h becombined with the herbicidal liquid at the initial point 15 fWatehsoluble hheal' P l/ he added as the ahtl'mlst of spraying byintroducing the polymer into the spray lhg e nozzle or even the nozzleorifice from some outside rese e y e t 0 1 s lutlon is meant aherbiervoir. The most practical method of incorporation of e hquldeohtalhlhg a hyereeafheh eohstlthehh as the polymer into herbicidalsolution involves a treatment of pfllhary eempteheht, e agalh Includes 1the solution prior to the actual spray step. The polymer sions. Such o1lsolut1ons normally contain at least 50% is preferably dissolved in theherbicidal solution and by welghttof 011 and more Often 60% Pl e If Suchhomogeneously dispersed throughout by conventional mix- 15 to be treatedWlth ah ahtl'fogglhg P ing techniques. This may be accomplished at anytime 15 agaln greatly Preferred that the P l be Soluble prior to spraybreakdown of the herbicidal solution phase m 011 of hydrocarbon Phaseaehleve best resultsinto actual spray droplets. One convenient method isto AS P e of an aqueous Fohltloh, the oll'hased dissolve the polymerinto the herbicidal solution just imherblcldal hquld, F eohtam mlhehamounts of other mediately before application For example, the actualsolvents or additives such as organic solvents, for exmixing operationmay be ellected upon a moving vehicle ample aICQhOIS, f eters,Emulslfylhg agents, such as a railroad car Which is used to Spray thePattie surface-active chemicals, disperslng aids, etc., may also ulararea to be controlled. It is understood, of course, form Pomon 0fherblcldal Seluhoh- For example, that the herbicidal process of theinvention may be cardetergent-type Wethhg g t s may be employed as forried out by either spraying undesirable vegetation while example thoseflescribed the artlcle ehmled Deterin growth stage or spraying theground prior to plant gent? and Ehulslfiers h John Mccuteheohyemergence. Oil-containing herbicidal solutions as straight oil solu-Depending upon the nature of the polymer, its mo1ec trons, oil-in-wateremulsions, and water-ln-oil emulsions, ular configuration, molecularweight, etc., use dosages may be made of a vanety of hYdmcarbfms orpetroleum may be varied over a considerable range. It is preferredploducts Suqh a f i mmeral 'f gas that the viscosity of an aqueousherbicidal concentrate 3 li dlsnnates In ln.any.lns.tances the not beincreased more than 20 centipoises after addition 40 i i iz g caimer l 32 of polymer. The dosages of polymer can be therefore ad- Lh h d nhpar 1as p at justed within these limits. Excessive dosages of high h rocarOHS t at best for provldmg oll'based molecular weight polymer have thetendency in most g l g cpnqerltrates Whlch may be subsequenlly instancesto increase the viscosity beyond the above stated 6 ann'H.nSt11ng i farehydroc.arbon oils which range, and should be avoided. In the case ofa primarily gi i f z sgigf 3:225: 2 555 33 1 hydrpphfablc or oll'based501mm, ,scoslty eludes those particular petroleum type solvents whichnot be 1n creaed Flore than loo centlpolses' Wlth t 6 contain at least5% by weight of aromatic components above points 1n m1nd generally 1nthe most preferred and most preferably, by Weight or more ExamplesPractice of the lhvehhoh from about 10 to about 1000 of solvents of thistype are listed in Table I below. For P-P- of high molecular Weight P yare added convenience, the specifications of these typical industrialherbicidal liquid. Within this range, misting or fogging 50 aromatictype oils are included.

TABLE I Specifications Composltwns A B C D E F G H Pale Amber. 78 F.

is at the very minimum substantially reduced. In some instances suchundesirable phenomenon has been completely corrected. The target of theherbicidal solution thus reaps the exclusive benefit of herbicidalcontrol without undesirable side effects of injury to crops anddesirable plant species. Likewise, fear of injury to animals who mayfeed upon herbicidally contacted non-target The most effective oil-basedherbicidal liquids which 7 0 may be treated in the instant inventioncontain oils which emulsifiable in aqueous or hydrocarbon solvents ormixtures or emulsions thereof. Specific herbicidal liquid concentrateswhich may be sprayed in the presence of high molecular weight polymerinclude the following representative classes; such substituted uracils'as -bromo-3-sec unsaturated group to yield a water-dispersiblesynthetic polymer having a structure substantially free of crosslinkage.The polymer is therefore available for solubilization or sufiicientdispersion in the particular aqueous butyl-methyl uracil, such arylalkyl urea herbicides as 1- 5 liquid to be treated. Treating agentsfound to be especially phenyl-3-methylurea, 1-(3chloro-4-methoxyphenyl)-3,3- effective for the purpose of the inventionof rendering dimethylurea, 1-(3-chlorophenyl)-3,3-dimethylurea, 1-(3,aqueous-herbicidal solutions non-misting are water-dis- 4dichlorophenyl)-3,3-dimethylurea, and 1-phenyl-3,3-dipersible syntheticpolymers having a linear hydrocarbon methylurea; acidic herbicides suchas 2,4-dich1orophenstructure and containing in a side chain, ahydrophilic oxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid, 2,4,group from the class consisting of carboxylic acid, car-S-trichlorophenoxyacetic acid, 3,4-dichlorophenoxyacetic boxylic acidanhydride, carboxylic acid amide, hydroxy, acid, 4-chlorophenoxyaceticacid, 2-(2,4-dichloropheev pyridine, pyrrolidone, hydroxy alkyl ether,alkoxy, carnoxy)propionic acid, 2-(2-methyl-4-chlorophenoxy) proboxylicacid salt groups, and mixtures of said groups.

pionic acid, 2-(2,4,5-trichlorophenoxy) propionic acid, Broadlyspeaking, the polymer treating agents which 2-(3,4-dichlorophenoxy)propionic acid, 2-(4-chloroare effective for reducing drift of aqueousherbicide soluphenoxy) propionic acid, 4-(2,4-dichlorophenoxy) butionsfall into three classes; namely, (1) those consisting tyric acid,4-(2-methyl-4-chlorophenoxy)butyric acid, 4- of polymeric organicsubstances which in an aqueous me- (2,4,5-trichlorophenoxy) butyricacid, 4-(3,4-dich1 orodium will form organic anions having a substantialnumphenoxy) butyric acid, 4-(4-chlorophenoxy) butyric acid, ber ofnegative electrical charges distributed at a pluraltrichloroacetic acid,2,2 iichloropropionic acid, 2,2,3- ity of positions on the polymer; (2)those consisting of trichloropropionic acid, 2,3,6-trichlorobenzoioacid, 2,3, polymeric organic substances which in an aqueous me-5,6-tetrachlorobenzoic acid, N-l-naphthylphthalamic acid, dium will formorganic cations having a substantial num- 2,6-endoxohexahydrophthallicacid, isopropyl xanthic ber'of postive charges distributed at aplurality of posiacid, monomethylarsonic acid, polychlorobenzoic acid,tions on the polymer; and (3) those consisting of polysuch substitutedpicolinic acids as 4-amino 3,5,6-tn'chloro meric organic substanceswhich in an aqueous medium picolinic acid and pentachloropentadienoicacid; salts, will not form ions but nevertheless contain a suificientesters, amides of any of the foregoing herbicidal acids or number ofhydrophilic groups to be water-dispersible. The others; maleic hydrazideand its herbicidal derivatives; first class of materials is referred toherein as anionic polychlorophenols (3 to 5 chlorine atoms) and theiralorganic polymers, the second class is referred to herein kaline salts;sulfamic acid and its salts; alkaline salts of as cationic organicpolymers, and the third class is recyanic acid; alkaline salts ofthiocyanic acid; alkaline ferred to herein as non-ionic organicpolymers. The first salts of arsenous and arsenic acids; sodium borates;soditwo classes can also be referred to as polyelectrolytes.

um or calcium cyanamide; phenyl mercury salts (acetate, The termpolyelectrolyte is intended to cover synoleate, formate, lactate,chloride, phosphate, and 'thethetic organic polymers which in an aqueousmedium will like); isopropyl esters of phenyl-v and..chlorophenylcarform organic ions having a substantial number ofelecbamic acids; 1,2,4-trichilorobenzene; dinitrophenols (ditricalcharges distributed at a plurality of positions.

nitro-o-cresol and dinitro-o-butyl-phenol) and their salts; Thesynthetic organic polymers containing only carboron trifluoride aminecomplexes; amino substituted sboxylic acid, carboxylic acid anhydride,and carboxylic triazines such as 2-chloro-4,6-bis(ethylamino)-s-triazine, acid salt groups in a side chain are anionic.The synthetic 2-chloro-4, ethylamino-6, isopropylamino-s-triazine, 2- 40organic polymers containing only pyridine or other simmethoxy-4,6-bis(isopropylamino)-s-triazine, 2-chl0r0 -4,,.., illrnitrogen-containing nuclei are cationic. The synthetic6-bis(diethylamino)-s-triazine, etc., and various combinaorganicpolymers containing only a carboxylic acid amide, tions of the justmentioned herbicides and others. pyrrolidone, a hydroxy, a hydroxy alkylether and/or an As mentioned above, the mist-decreasing polymers ofalkoxy group in a side chain or non-ionic. The invention the inventionshould have a molecular Weight'in excess of contemplates the employmentof P y Which Contain 100,000. Greatly preferred polymeric additives havea v anionic, cationic and/or non-ionic groups. It also conmolecularweight of at least 300,000. In many instances templates the employmentof mixtures of anionic, cationic the molecular weight of the polymeradditives ranges as and/ or non-ionic water-dispersible syntheticorganic polyhigh as 1-10 million or more. mers.

If the herbicidal liquid to be treated is aqueous in T e owing syntheticOrganic polymers and their nature or an oil-in-water emulsion, thepreferred polcharacteristic groupings illustrate the types of polymersymeric structures are derived by the polymerization of which have beenfound to be effective for the practice of at least one mono-olefiniccompound through an aliphatic the invention:

' TABLE II Number Name Characteristic Grouping 1 Polyacrylate sodium salCHr-OH' 2 Polymethacrylic acid sodium salt; CH; CH2- I Ng,(+)

3 Maleic anhydride-vinyl acetate eopo1ymer--.,-. -CH-CHaOH-C H 5 4. i=0omh=o 0 o 4 Polyvinyl methyl ethermaleic anhydride OHOH:CHCH 0 (':=0oc'zn. 0 o

TABLE lIIC0ntlnued Number Name Characteristic Grouping 5 Methacryllcacld-aerylamlde copolymer OH; CH;

CH:( 3C Hr- C O O H C O NH:

6 Polyacryllo i C H:-C H- C O O 7 Isopropenyl acetate-malelc anhydrldesodium salt copolymer. CH,

CH|( J--CHC H- =O (i=0 CH,( J=0 5H 6 N m m s Itaconlc acid-vinyl acetatecopolymer C O O H COH:CH:CH-

H C HC=0 9 Polyvinyl pyrldine-hydro CHr-CH- 10 a-methyl styrene-malelcanhydrlde sodium salt copolymer CH;

1 -3-CHg-CH--CH- COO (300 11 Polyvinyl pyrrolldone H IL 1120 \C=O H:(--(!7 12 Styrene-malelc anhydrlde sodlum salt copolymar -OHCH,CH---GHCOOP COOP N m m 13 Polyvinyl alcohol. -CHCH 14 Polyvinyl methyl ether--CH-CH,-

15 Methylmethacrylate-malelc anhydrlde sodium salt copolymer... CH;

-( 3--CHz-GH CH- (BOOCH; COO 600 N N m 16 Polyvinyl acetate emulsion--CHCH;

CHxC I=O 17 Acryllo acid-styrene copolymar --CH-OH,CH- --cH- C 0 O H Anyof the polyelectrolytes disclosed in United States Patent No. 2,625,529can be employed for the purpose of the invention. When the copolymersare identified in terms of their monomeric constituents, it should beunderstood that the names applied to these copolymers refer to themolecular structure and are not limited to the polymers prepared by thecopolymerization of specific monomers. In many cases, the identicalcopolymers can be prepared from other monomers and converted bysubsequent chemical reaction to the desired copolymer.

Where the copolymer is derived from a polycarboxylic acid derivative andat least one other monomer copolymerizable therewith, the polycarboxylicacid derivative may be maleic anhydride, maleic acid, fumaric acid,itaconic acid, aconitic acid, citraconic acid, the amides of theseacids, the alkali metal (e.g. sodium, potassium and lithium), thealkaline earth metal (e.g. magnesium, calcium, barium and strontium),and ammonium salts of these acids, the partial alkyl esters (e.g.methyl, ethyl, propyl, butyl, mono esters), the salts of said partialalkyl esters, and the substituted amides of these polycarboxylic acids.Where the hydrophilic maleic acid derivatives are used as one of thestarting components to form the copolymer, the hydrophobicvcomonomersmay be, for example, styrene, alphamethylstyrene, vinyl toluene,chlorostyrene, vinyl acetate, vinyl chloride, vinyl formate, vinyl alkylethers, alkyl acrylates, alkyl methacrylates, ethylene, propylene,and/or isobutylene.

Y The foregoing synthetic copolymers are preferably obtained by reactingequimolar proportions of a polycarboxylic acid derivative and at leastone other monomer. However, certain of the hydrophilic derivatives ofunsaturated polycarboxylic acids can be polymerized in less thanequimolar proportions with some of the less hydrophobic comonomers, forexample, vinyl formate and vinyl acetate.

In addition to bomopolymers and copolymers of any of the just mentionedmonomers, combinations thereof or others, terpolymeric substances maylikewise be usually employed in reducing mist of sprayed herbicidalliquid concentrates. A greatly preferred group includes polymerizedacrylamide as one of the components of either a copolymer or terpolymer.Usually the copolymer or terpolymer contains acrylamide as a majoringredient. Greatly preferred polymers include acrylamide-acrylic acidcopolymers, and acrylamide-maleic acid-methacrylic terpolymers.

In addition to the above described results with cationic and anionicorganic materials, highly desirable results have been obtained when highmolecular weight ethylene oxide polymers are used. These polymers have aviscosity in centipoises at 25 C.,'of from 500 to 30,000 when made up inone-half to five percent aqueous solutions. For best results, suchpolymers should have molecular Weights in excess of one million. Thelower molecular weight materials have molecular weights starting about200,000. These polymers are prepared by heating appropriate quantitiesof ethylene oxide with initiating molecules such as ethanol, ethyleneglycol and the like in a sealed tube for six hours or more in thepresence of a catalyst. Suitable catalysts include alkaline earth metalcarbonates such as strontium or calcium carbonate. While ethylene oxidecondensate polymers are the most preferred materials, other non-ionic,polypolar polymers are not precluded from use in the invention. Theexpression polypolar polymers refers to polymers having a plurality ofnon-ionized groups whereby said polymers are rendered hydrophilic. Suchcompounds for use with this invention desirably include polyacrylamide,poly-substituted acrylamides, polyvinyl alcohols, polyvinyl pyrrolidonesand polyvinyl oxazolidones, as mentioned above.

Organic polymeric coagulants of vegetable and cellulosic origin may alsobe used in the newly invented process covered in this application. Theseinclude water-soluble or dispersible starches, starch derivatives,dextrans,

phosphated starches, Gum Ghatti, Jaguar, Locust Bean Gum, carboxy methylcellulose, and other well-known high-molecular weight water-solublevegetable gums and their derivatives.

When liquid oil concentrates of herbicides or water-inoil emulsions areto be treated, it is greatly preferred that the polymeric anti-foggingagent he soluble in the oil component. It is therefore preferable thatthe polymer be derived from a hydrophobic monomer. Examples typical ofthese are styrene, alpha-methylstyrene, vinyl toluene, chlorostyrene,vinyl acetate, vinyl chloride, vinyl formate, vinyl alkyl ethers, alkylacrylates, alkyl methacrylates, ethylene, propylene, n-butylene,isobutylene, etc. The most preferred oil-soluble polymers have amolecular Weight in excess of 100,000 and most preferably at least300,000. Those polymers which have shown the greatest measure of successhave a linear hydrocarbon structure derived from an ethylenicallyunsaturated monomer containing 2-5 carbon atoms. These monomers maycontain one or two unsaturated groups. Among these, polyethylene,polypropylene, polyisobutylene, polybutadiene, polyisoprene andcopolymers thereof have shown the most promise. P-olyisobutylene andpolyisoprene (natural rubber) are the most preferred of this group.

It has been discovered that the instant process is adaptable for avariety of spray operations other than spraying of herbicidal liquids.The following are illustrative of just a few spraying operations whereincorporation of an antimisting polymer prevents undesirable fogging ormisting: in metal cleaning, washing and processing; in water-downoperations on roadways and similar areas; in washing and coolingapplications; in cooling with oil in a variety of industrialapplications; for use in a variety of industrial Washing machines; insteel mill applications;in said, coal, gravel, and dish Washing; inasphalt spraying and other industrial applications of this type; infresh stone and gravel washing; in degreasing; for use in sprayingliquids into mixing tanks; in spraying eliminator plates; in coolingconveyor belts; in film Washing; in spray cooling; in lubricantspraying; for use in air washers; for foam control; in humidifying; foruse in desuperheating steam in pipes; for spraying inside ducts andpipes, in coke quenching; in cooling via heat exchangers; in pulpwashing; for absorption stack spraying; in tank cleaning; in washing ofmine and quarry products, fruits and vegetables; in spray drying avariety of products; for use in packing-house brine spray coolingsystems; in brine spraying; in tubular unit coolers; for roof cooling;in Wetting operations; in mist cooling; in evaporative cooling; for usein Water display fountains; for spraying insecticides, liquidfertilizers and other pest control reagents; for use in fuel injectionprocesses; for use in aerosol spray containers; in flash evaporatingmethods; in automatic car washing techniques; etc. In any of the justmentioned spraying operations or others of a similar nature, the liquidto be sprayed may be treated as exactly outlined with respect tospraying of herbicidal liquids. Equally good results of substantialreduction in misting and fogging may be obtained in these just mentionedprocesses.

By the term soluble, as applied to the property of the polymers of theinvention of being able to be incorpo rated into herbicide or othersolutions, is meant the ability of being solubilized or dispersed in atleast use amounts in the liquid being treated.

It is not totally understood how the just mentioned polymers or othersfalling within the defined group of workable materials aid insubstantially reducing misting or fogging of sprayed solutions even whenapplied in relatively minute amounts. Without polymer present during aspraying operation a pressure drop occurs in which excess energy presentactually fractures the liquids into mist or fog. When the polymer isadded to the sprayed solution it is believed a visco-elastic elfecttakes place. That is to say, the polymer-treated liquid actually isdeformed in a visco-elastic manner which allows the energy from thepressure drop to fracture the liquid in a more uniform manner, andprevent formation of very small droplets. This occurs rather than thespray breaking up into a mist pattern. In essence, shock or energy istaken up by a polymer-treated liquid in contradistinction to anuntreated solution which is incapable of resisting the shock or energywithout substantially changing its rheological characteristics.

It was noted that in spraying polymer treated herbicidal solutions andother treated solutions, a variety of advantages other than mistreduction are present. For example, uniformity of spray pattern as wellas droplet size is achieved. In addition, concentration of spraypressure at point of impact is increased. Such effect may beparticularly useful in cleaning, descaling, etc., operations.

In order to determine the efficacy of the invention, certain spray testswere devised. In the first series of tests, water was sprayed as thebase fluid at a spray nozzle pressure of 50 p.s.i., without additive andwith various polymers at varying dosage levels. Table III below showsthe results of these tests.

In all of the above tests, the polymer antimisting agent had a molecularweight in excess of 100,000, and in most instances had molecular weightsof a much higher magnitude. For example, the polyoxyethylene treatingagent had a molecular weight estimated to be approximately 7 million.Likewise, the acrylamide homopolymer and acrylamide-based terpolymermaterials had molecular weights of approximately -10 million.

In another series of tests a high aromatic content oil which isgenerally used as a phytotoxic carrier for other herbicides was alsosprayed. Considerable drift was noted without benefit of polymeradditive treatment. When a high molecular weight polyisobutylene wasadded to the oil in a dosage amount of 400 p.p.m., a considerablereduction of misting of the oil system was noted.

In further experimentation, various runs were initiated to determine ifthe through-put of a nozzle was affected by addition of polymer.Specifically, the terpolymer of acrylamide-methacrylic acid-maleicanhydride was added to water at various additive levels and compared tothe through-put for a non-treated water sample. A blank of 75 ml. ofwater had a through-put time of 4.5 seconds at 40 p.s.i. At the 200p.p.m. additive level of polymer, the through-put of the 75 ml, ofpolymer treated water was 4.4 seconds; at 400 p.p.m. the through-put was4.3 seconds, and at 800 p.p.m. the through-put time for 75 ml. oftreated water was 4.0 seconds. Thus, it is seen that not only was thethrough-put unaffected, but actually the efiiciency of the sprayingoperating increased due to increase in through-put per unit time ofpolymer-treated water solutions.

The following examples further illustrate the utility of the invention.Specifically, in the following tests, herbicidal solutions of both oiland water types were sprayed in the presence of various polymericsubstances. In each case, a definite decrease of misting or fogging wasnoted when compared to like spraying involving no polymer.

12 EXAMPLE I A 1% solution of sodium trichloroacetate heribicide wasapplied to oats and millite via sprayings with and without a polymer. Inthe series of runs in which polymer was present, 200, 400 and 800 p.p.m.of an acrylamidemaleic anhydridemethacrylic acid terpolymer was added tothree portions of the herbicidal aqueous liquid. The followingobservations were made. It was noted that a definite increase inretention of the spray liquid was present in all three liquidscontaining anti-misting polymer. The retained spray was in the form offairly large droplets. After approximately one weeks time, it was notedthat the herbicidal activities of all trial spray runs with and withoutadded polymer were essentially the same.

EXAMPLE II In this example an approximate 1% oil-in-water emulsion ofpentachlorophenol solution was sprayed alone and in presence of theabove described terpolymer. The polymer treated spray solution had asubstantially reduced mist pattern in all cases.

EXAMPLE III A herbicidal oil solution was made up containing thefollowing described components. The oil was itself phytotoxic in natureand contained approximately 45% aromatics. Into this oil was dissolved1.9% of the propylene glycol butyl ether ester of 2,4,5-trichlorophenoxyacetic acid. This particular herbicidal oil solution was tested in afield application, and specifically sprayed upon dormant brush growingalong a roadside. Without benefit of polymer treatment, it was notedthat the spray blew in a wide pattern, and even across the entire roadwidth. With an incorporation of approximately 400 p.p.m. of apolyisobutylene polymer having a molecular weight of approximately350,000, a thus treated oil solution containing the above herbicidecomponents was sprayed in a comparative application. In this instance adefinite reduction in drift was noted and at no time did the spray blowany appreciable distance.

EXAMPLE IV 20 lbs. of 2,2-dichloropropionic acid was dissolved ingallons of water. This substance was sprayed along a railroadright-of-way in a southern area of the United States. Specifically,Johnson grass was the undesirable vegetation being treated, andnoticeable misting occurred in the spray operation. When 200 p.p.m. ofthe terpolymer of Example I was mixed into the liquid herbicidesolution, misting or fogging of the thus benefitted herbicidal solutionwas almost completely obviated. The same phenomenon of polymer benefitwas noted in spraying 60 lbs. of sodium trichloroacetate dissolved in100 gallons of water and 100 lbs. of sodium chlorate dissolved in 100gallons of water.

EXAMPLE V Approximately a 1% oil-in-water emulsion of pentachlorophenolwas made up. To this was added both 3 -chlorophenyl)-1, 1 dimethyl ureaand 2-chloro,4-ethylamino, 6-isopropylamino s-triazine. The two abovematerials were suspended in the oil and water emulsion, and the entiresolution mixture sprayed with and without benefit of the terpolymerdescribed in Example I.

It was noted that considerable drift occurred without polymerapplication, while inclusion of approximately 100 p.p.m. of terpolymersubstantially reduced spray drift.

EXAMPLE VI Into the oil described in Example III was dissolved 3.4% ofthe isooctyl ester of 2(2,4,5-trichlorophenoxy) propionic acidherbicide. This oil solution was again sprayed with and without benefitof polyisobutylene (molecular weight=300,000; 400 p.p.m. treatmentlevel). The same results were noted as set out in Example HI.

The above examples are intended to illustrate the process of theinvention, and are not intended to be limitative thereof. Othermodifications and variations of the invention will be apparent to thoseskilled in the art.

The invention is hereby claimed as follows:

1. A method of controlling the growth of undesirable vegetation whichcomprises the steps of spraying aqueous solutions which contain:

(a) a phytotoXic amount of a herbicide, and

(b) dissolved therein at least 10 parts per million, but

yet a substantially non-viscosity increasing amount of a water solublepolymer formed by the polymerization of at least one monoolefiniccompound through an aliphatic unsaturated group and have a molecularweight of at least 100,000, said liquid being characterized as havingreduced misting tendencies when sprayed.

2. The method of claim 1 where the water soluble polymer has a linearhydrocarbon structure which contains in a side chain a hydrophilic groupselected from the class consisting of carboxylic acids, carboxylicanhydride,

carboxylic acid amide, hydroxy, pyridine, pyrrolidone, hydroxy alkylether, alkoxy, carboxylic acid salt, and mixtures of said groups.

3. The method of claim 2 where the Water soluble polymer has a molecularweight of at least 300,000.

References Cited UNITED STATES PATENTS 2,652,322 9/ 1953 Hedrick et al71-2.7 3,045,394 7/1962 Coulter 71-2.1 X 3,067,089 12/1962 Winslow167-42 3,158,535 11/1964 Beerbower et al. 16742 3,131,119 4/1964 Fordyceet 211.

3,175,898 3/1965 Seymour et a1. 71-27 3,235,366 2/1966 Seymour et a1.71--2.6

FOREIGN PATENTS 831,344 3/ 1960 Great Britain.

20 JAMES O. THOMAS, 111., Primary Examiner.

A. J. ADAMCIK, Assistant Examiner.

Patent No. 3,360,356

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION December 26, 1967Joseph F. Vartiak It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected asshown below:

Column 11, TABLE III, third column, line 2 thereof, "Do." should readVery little mist.

Signed and sealed this 2nd day of December 1969.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Commissioner of Patents Edward M. Fletcher, Jr. Attesting Officer

1. A METHOD OF CONTROLLING THE GROWTH OF UNDERSIRABLE VEGETATION WHICHCOMPRISES THE STEPS OF SPRAYING AQUEOUS SOLUTIONS WHICH CONTAIN: (A) APHYTOTOXIC AMOUNT OF A HERBICIDE, AND (B) DISSOLVED THEREIN AT LEAST 10PARTS PER MILLION, BUT YET A SUBSTANTIALL NON-VISCOSITY INCREASINGAMOUNT OF A WATER SOLUBLE POLYMER FORMED BY THE OLYMERIZATION OF ATLEAST ONE MONOOLEFINIC COMPOUND THROUGH AN ALIPHATIC UNSATURATED GROUPAND HAVE A MOLECULAR WEIGHT OF AT LEAST 100,000, SAID LIQUID BEINGCHARACTERIZED AS HAVING REDUCED MISTING TENDENCIES WHEN SPRAYED.